Numerical and experimental investigation on the flexural stiffness of RC beams strengthened with prestressed CFRP plate exposed to wetting/drying cycles

The load-deflection relationship is critical for the serviceability and structural durability of reinforced concrete (RC) structures strengthened with prestressed carbon fiber-reinforced polymer (CFRP) plates. This study aims to investigate the impact of prestressing levels and wetting/drying cycles (WDCs) on the flexural stiffness of prestressed CFRP-strengthened RC beams. A modified flexural stiffness prediction model was proposed by incorporating prestressing levels, interfacial bond slip, and softening after WDCs. Subsequently, four-point bending tests were conducted on 11 strengthened beams with different prestressing levels and WDCs to estimate flexural behavior. The results suggest that WDCs can adversely affect the flexural stiffness of the strengthened beams, particularly for the post-cracking stiffness of the non-prestressed specimens. However, prestressed strengthening can mitigate the stiffness degradation caused by WDCs. Moreover, a finite element (FE) model utilizing a traction separation model can accurately predict flexural stiffness. Finally, the flexural stiffness was computed using both the existing and proposed models and the proposed model provides the closest prediction of the flexural stiffness for CFRP-strengthened beams under WDC and prestressing

Estimation of Airflow Parameters for Tail-Sitter UAV through a 5-Hole Probe Based on an ANN

Fixed-wing vertical take-off and landing (VTOL) UAVs have received more and more attention in recent years, because they have the advantages of both fixed-wing UAVs and rotary-wing UAVs. To meet its large flight envelope, the VTOL UAV needs accurate measurement of airflow parameters, including angle of attack, sideslip angle and speed of incoming flow, in a larger range of angle of attack. However, the traditional devices for the measurement of airflow parameters are unsuitable for large-angle measurement. In addition, their performance is unsatisfactory when the UAV is at low speed. Therefore, for tail-sitter VTOL UAVs, we used a 5-hole pressure probe to measure the pressure of these holes and transformed the pressure data into the airflow parameters required in the flight process using an artificial neural network (ANN) method. Through a series of comparative experiments, we achieved a high-performance neural network. Through the processing and analysis of wind-tunnel-experiment data, we verified the feasibility of the method proposed in this paper, which can make more accurate estimates of airflow parameters within a certain range

Solution-Phase Chelators for Suppressing Nonspecific Protein−Metal Interactions in Electrospray Mass Spectrometry

Protein-metal complexes may be transferred from solution into the gas phase by electrospray ionization (ESI), such that they can be directly analyzed by mass spectrometry (MS). In principle, therefore, ESI-MS represents a simple and elegant approach for gaining insights into the binding stoichiometry and affinity of these assemblies. Unfortunately, the formation of nonspecific metal adducts during ESI can be a severe problem, often leading to binding levels that are dramatically higher than those in bulk solution. Focusing on several calcium binding proteins as test systems, this work explores the suitability of different salts to serve as metal source. Despite their widespread use in previous ESI-MS studies, calcium chloride and acetate induce extensive nonspecific adduction. In contrast, much lower levels of artifactual metal binding are observed in the presence of calcium tartrate. In the case of high and intermediate affinity proteins, the resulting ESI-MS data are in excellent agreement with the calcium binding behavior in bulk solution. The situation is more challenging when studying proteins with very low affinities, but in the presence of tartrate qualitative information on protein-metal interactions can still be obtained. The beneficial effects of tartrate also extend to zinc binding experiments. This work does not directly explore the mechanism by which tartrate suppresses nonspecific metalation. However, it seems likely that weak chelators such as tartrate sequester metal ions within rapidly shrinking droplets during the final stages of ESI, thereby reducing nonspecific metal adduction to protein carboxylates. The use of tartrate and possibly other weak chelators will greatly enhance the reliability of future ESI-MS studies on the interactions of proteins with divalent metal ions

Evaluation of red and near infrared fluorescent silver nanoclusters as potential in vivo indicators of tight junction opening

Tight junctions (TJs) play a key role in regulating permeability to liquids, ions and larger solutes through the paracellular route. To demonstrate TJ structure changes by measuring paracellular flux is challenging for understanding biological functions of tight junction and designing delivery system for highly hydrophilic macromolecular drugs. In the present study, we tested two long wavelength emitting silver nanoclusters (AgNCs), Ag2S(BSA)-NCs (lambda(ex/em) at 500/1050 nm) and Ag(GSH)-NCs (lambda(ex/em) at 488/640 nm), for their suitability as novel paracellular permeation indicators on a MDCK monolayer. Ag2S(BSA)-NCs exhibited marginal cytotoxicity and passed through the cell monolayer exclusively via the paracellular pathway. However, Ag(GSH)-NCs could be taken inside the cells possibly through endocytosis. AgNCs together with Eu-DTPA were used in the double probe strategy for detecting the change of TJ pore path parameters (i.e. pore size r and retention capacity epsilon/tau) upon TJ opening with EDTA or vanadyl acetylacetonates, respectively. The AgNCs/Eu-DTPA probe set was found to give the same results as our previous work using the short wavelength emitting AuNCs and Eu-DTPA probe set, suggesting future potential applications of AgNCs to the in vivo studies of TJ alternations upon stresses. This work reinforced the use of a double probe set for study of the TJ structure change

Heteroplasmy and Individual Mitogene Pools: Characteristics and Potential Roles in Ecological Studies

The mitochondrial genome (mitogenome or mtDNA), the extrachromosomal genome, is a multicopy circular DNA with high mutation rates due to replication and repair errors. A mitochondrion, cell, tissue, organ, or an individual body may hold multiple variants, both inherited and developed over a lifetime, which make up individual mitogene pools. This phenomenon is also called mtDNA heteroplasmy. MtDNA variants influence cellular and tissular functions and are consequently subjected to selection. Although it has long been recognized that only inheritable germline heteroplasmies have evolutionary significance, non-inheritable somatic heteroplasmies have been overlooked since they directly affect individual fitness and thus indirectly affect the fate of heritable germline variants. This review focuses on the characteristics, dynamics, and functions of mtDNA heteroplasmy and proposes the concept of individual mitogene pools to discuss individual genetic diversity from multiple angles. We provide a unique perspective on the relationship between individual genetic diversity and heritable genetic diversity and guide how the individual mitogene pool with novel genetic markers can be applied to ecological research